A variety of medical imaging modalities, for example computerized tomography (CT), magnetic resonance imaging (MRI) and positron emission tomography (PET), have become standard techniques in obtaining medical imaging data representative of a patient or other subject for diagnostic or other purposes. Medical imaging data can be in a variety of forms and can for example include any suitable data obtained from measurements by a medical imaging modality and/or any suitable data representative of one or more anatomical features. Medical imaging data may be any data that can be rendered, or otherwise processed, to obtain an image of at least part of a patient or other medical subject and/or any data that can be rendered, or otherwise processed, to obtain an image of one or more anatomical features. Volumetric medical imaging data may, for example, be in the form of an array of voxels. Such arrays of voxels may for example be representative of intensity, absorption or other parameter as a function of three-dimensional position, and may for example be obtained by suitable processing of measurement signals obtained by a medical imaging modality.
The wrist is one of the most intricate articulations of the musculoskeletal system. The wrist comprises eight small bones (the carpal bones) and a complex intrinsic and extrinsic ligament system, which is illustrated in FIG. 1. FIG. 2 shows the eight small carpal bones 10A to 10H together with parts of the radius 12 and ulna 14 (the bones of the forearm). FIG. 2 also shows parts of the metacarpal bones 16.
Because of the complexity of the wrist, injuries to the bones or ligaments of the wrist may potentially cause irreversible disruption to the movement of the wrist, and may initiate progressive osteoarthritis.
It is known to study the movement of the wrist by taking a series of images of the wrist, each image being taken with the wrist at a different position. For example, the wrist may be moved such that the hand moves from side to side in the plane of the hand, as in a waving motion (this motion may be referred to as radial-ulnar deviation). The movement of the wrist may be studied to provide a comparison of the movement pre- and post-treatment, for example to determine a change in movement due to surgery.
In certain contexts, a neutral phase of a wrist movement may be taken as being the midpoint between the two extremes of motion (or may be taken as being in some other position in other contexts). Textbook drawings and other anatomical drawings of the wrist may in general be presented in neutral phase. For example, FIGS. 1, 2, and 3 show a wrist presented in neutral phase.
Presentation of data using techniques typical of illustrative anatomical drawings (for example, presentation of the bones of a joint in an exploded or disarticulated view) can provide further information about a joint and shed further light on pathologies. An example of such a presentation is shown in FIG. 4. Preparing such visualizations can be a time-consuming and labor-intensive task.
The analysis of the kinematics of the wrist joint and the analysis of individual bones in the wrist may be difficult and time-consuming. Bones of interest may be required to be identified manually. The neutral phase may be required to be identified in a series of images taken at different phases of motion. Pathology may need to be identified. Pre- and post-treatment images may be compared. The analysis may be made more complicated by the presence of malformations.
Appropriate presentation and visualization of patient volumetric data can improve reading time and improve diagnosis.
FIG. 5 shows a scan image of a patient's wrist. It may in some circumstances be difficult for a clinician to obtain all the information that he or she may desire from a scan image such as that of FIG. 5. In some circumstances, pathology, trauma and scanning condition can hinder clear visualization of patient anatomy.
It is known to create atlases of the human anatomy, or atlases of particular parts of the human anatomy. Known atlases comprise a set of voxels, each voxel comprising image intensity and position data, and may further comprise position data indicating the position of particular anatomical features in the atlas. It has also been suggested to include other statistical measures relating to intensity in an atlas.
Atlases may be used in the processing or analysis of imaging data obtained by measurements on a patient. It is known to register imaging data to atlas data using rigid, affine or non-rigid registration, thereby obtaining a rigid, affine or non-rigid transformation which may be applied to the imaging data to align anatomical features in the imaging data with corresponding anatomical features in the atlas. A rigid registration may comprise translation and/or rotation. An affine registration may comprise translation, rotation, scaling and/or shearing.
Techniques for registration of images are well-known. In general, registration is an optimization problem, with the aim of finding an optimal transformation between two sets of imaging data. The transformation relates corresponding features in the sets of imaging data by mapping points in the coordinate system of one set of imaging data onto the corresponding points in the coordinate system of the other set of imaging data. The optimal transformation may be determined by maximizing (or minimizing) a similarity measure, for example mutual information.
The use of such atlases and registration procedures may enable, for example, direct comparisons to be performed between imaging data obtained from different subjects.
Segmentation is the process of identifying pixels or voxels representing a given structure in an image, which may include separating the pixels or voxels from the rest of the image. The structure may be, for example, an anatomical structure such as a bone, a vessel or an organ. The identification and/or separation of pixels or voxels representing the structure may facilitate further processing of information relating to the structure, for example, measurement of the structure, or rendering the structure in a way that is distinct from other structures in the image.